Calculate the number of atoms in 10 litres of ammonia [N = 14, H = 1]

1 mole of NH₃ = 1 N + 3 H = 4 atoms

= 4 × 6.023 × 10²³ atoms and occupies 22.4 lit at s.t.p.

22.4 lit of NH₃ has 4 × 6.023 × 10²³ atoms

⇒ 10 lit will have = 4 × 6.023 × 10^{23}\over22.4 × 10

= 40\over22.4 × 6.023 × 10²³

= 1.786 × 6.023 × 10²³

Hence, number of atoms in 10 litres of ammonia = 1.786 × 6.023 × 10²³ atoms